Earlier in vivo studies (Hemmings and Sims, Eur. J. Biochem., in press) suggested that the NAD-dependent glutamate dehydrogenase from the food yeast, Candida utilis, existed as two interconvertible forms, which could be rapidly inactivated and reactivated. The aim of this project is to elucidate the biochemical mechanism of interconversion. To date, the active form of the enzyme has been purified by affinity chromatography and conventional purification techniques: antibodies have been raised against this protein in sheep. We intend to further characterize and purify the active and inactive forms of the NAD-GDH and the proteins responsible for the interconversion.